In this project we have developed dendrimer based nanoparticles which are labeled with optical, radionuclide and/or MRI contrast agents for use in sentinel node imaging in animal models of metastatic disease and eventually in humans. The purpose of this research is two fold. First, is to develop a better imaging agent for sentinel node imaging, one that combines two imaging modalities rather than the current method that requires two separate injections. This will lead to reduced morbidity of sentinel node resections and improve their reliability. An additional purpose is to investigate the mechanisms by which the lymphatics act as conduits for metastatic disease and how this process could be monitored and interfered with. We intend to develop the next generation of sentinel node imaging agents that are not merely passively targeted to the lymph node but actively targeted to metastases within the lymph node. Towards that end we have labeled the dendrimer nanoparticle with Fab Herceptin and will investigate other targeting ligands. We also hope to develop methods of evaluating lymphedema in human subjects to reduce suffering due to this disorder.